When Zeta Global (NYSE: ZETA) reported first-quarter 2026 results on April 30, 2026, the headline was a 50% revenue increase to $396 million. But buried inside the financials was a more specific story: the agency channel had grown fast enough to move the company's cost structure, compress its EBITDA margin by 100 basis points year-over-year, and still add meaningfully to guidance confidence. Understanding exactly how that happened - and why management considered it a feature rather than a problem - requires tracing the mechanics of how agencies onboard to Zeta's platform and what they tend to buy first.

The cost-of-revenue signal

Zeta's GAAP cost of revenue in Q1 2026 was 41% of total revenue, up 190 basis points year-over-year and 50 basis points sequentially from Q4 2025. That increase was not a sign of operational deterioration. According to Christopher Greiner, Zeta's CFO, the driver was unambiguous: "The increase in cost of revenue was driven by new agency wins, driving a higher initial mix of social as a channel."

Social advertising carries a structurally higher cost of revenue than Zeta's owned-and-operated channels such as email, display, video, mobile, and connected TV (CTV). When a new agency comes onto the Zeta Marketing Platform, social is typically the entry point. Greiner explained why: Zeta offers a "substantially more efficient and effective solution for social," which makes it the first channel agencies migrate to the platform. The implication is that agencies arrive through a higher-cost door, then expand into Zeta's lower-cost owned channels over time.

That migration pattern shapes the financial trajectory. According to the earnings transcript, as new agencies scale, "not only does their aggregate spend increase, but they do so by adding Zeta-owned channels like e-mail, display, video, mobile, CTV and others." Each additional channel layered on top of the initial social relationship shifts the revenue mix toward lower-cost formats, improving margins incrementally as the agency relationship matures. Greiner was explicit that social, despite its higher cost of revenue, "is still accretive to both adjusted EBITDA and free cash flow margins" and "drives high customer stickiness."

Independent agencies: from zero to eight figures

The most striking individual data point on agencies came during the analyst Q&A. An RBC analyst asked specifically about independent agencies and the white-label opportunity. Greiner's answer was concrete. According to the transcript, "one of the key wins we had, Matt, in the quarter was with a large independent. If you look at business done a year ago with them was 0. Business done within this quarter was 8 figures with Athena being, again, something that was visible to them as something they could also exploit for their benefit."

Eight figures means at least $10 million of revenue generated within a single quarter from a relationship that did not exist twelve months earlier. That pace of ramp has specific implications for how Zeta's sales motion is working with the independent agency segment. The same exchange revealed a second data point: a separate large agency that had been piloting Zeta in 2025 at just under $2 million in spend signed a new agreement more than ten times that size.

Greiner also noted that among the five largest advertising holding companies, the number of brands working with Zeta grew by 50% year-over-year. David A. Steinberg, Co-Founder, Chairman, and CEO, said on the call that Zeta is now working with "pretty much all of the large holdcos."

Athena as the agency selling tool

The role of Athena by Zeta in these wins was raised explicitly on the call. Athena, which reached general availability on March 24, 2026, was cited as a "crucial differentiator versus incumbents and RFP competitors in each of our marquee enterprise and agency wins in Q1," according to Greiner. For independent agencies trying to compete with the resources of the major holding companies, a white-labeled AI platform that can reduce the labor intensity of managing a full-stack marketing operation represents a structural capability upgrade.

Steinberg addressed the white-label dynamic directly. According to the transcript: "We're actually big fans of the agencies. They provide incredible services to their clients. And we've had clients approach us to go direct. And we always try to bring the agency back into it because we think it's a very healthy relationship when it's the three of us." That framing positions Zeta's agency strategy as complementary rather than competitive - the platform handles the data, identity, and AI infrastructure, while the agency manages the client relationship and strategic layer.

The launch of Athena in March 2026 followed the introduction of AI Agent Studio in March 2025, which gave agencies an early look at what agentic orchestration could do inside the Zeta platform. Athena is the consumer-facing surface built on top of that infrastructure. For agencies specifically, the ability to white-label a product that compresses multi-team workflows into a single interface is a selling point in competitive pitches against larger holding company networks that have built their own technology stacks.

The competitive framing: agencies versus DSPs

An analyst from Canaccord Genuity opened the Q&A by asking Steinberg about the public backlash against the Trade Desk and the ad tech ecosystem, and whether Zeta had benefited from that dynamic. Steinberg was careful to distinguish between two separate categories. Agencies, in his view, "continue to thrive and they're not really having any issues from our vantage point." The criticism was aimed elsewhere: at "organizations that have built workflow management tools that do not have proprietary data, they do not have proprietary native artificial intelligence."

That distinction matters for how the agency story fits within the broader competitive picture. Zeta is not positioning itself against agency holding companies - it is positioning itself as the data and AI infrastructure that agencies deploy on behalf of their clients. The competitive pressure lands instead on legacy DSPs and standalone marketing clouds that compete with Zeta at the platform level rather than the agency services level.

Steinberg added a structural observation about the division of labor between Zeta and its agency partners. According to the transcript: "None of the agencies really focus on the retain, which, as of last quarter, is about 60% of our business. So we have real greenfield opportunity there as it relates to the activation, which sort of create customers, monetize customers." The retention use case - which includes loyalty, lifecycle marketing, and CRM - adjacent capabilities - is territory that agencies tend not to own deeply. Zeta sees that as an expansion surface where it can grow revenue within existing agency relationships without creating channel conflict.

Agency wins flowing into committed contracts - and RPOs

One consequence of the agency channel expansion that has not received as much attention is the shift in revenue visibility. According to Greiner, remaining performance obligations (RPOs) rose by $66 million from Q4 2025 to Q1 2026. He attributed part of that increase to agencies "beginning to now also sign long-term committed contracts." That is a structural change in how the agency revenue is being booked.

Agencies have historically been associated with shorter contract cycles and less committed forward revenue than direct enterprise software relationships. When agencies begin signing long-term contracts, that changes the visibility profile of that revenue segment considerably. Greiner said the RPO increase, combined with the Marigold contribution, gave Zeta the "confidence to be able to raise the guidance that we did on the top line by $30 million while continuing to keep to our 2% to 5% conservatism." In other words, the agency contract shift was one of the inputs that justified the guidance raise - not just the headline revenue beat.

The working capital cost of agency growth

Growing the agency channel has one mechanical side effect that Greiner acknowledged directly. Free cash flow in Q1 2026 was $41.7 million, representing a 63% conversion of adjusted EBITDA and a 270 basis point improvement year-over-year. But that figure, according to Greiner, "includes a roughly 13-point working capital headwind driven by longer agency payment cycles standard for their industry."

Agency payment cycles are structurally longer than direct enterprise cycles. When agencies intermediate between a brand and Zeta's platform, payment timelines extend. A 13-point working capital headwind on free cash flow conversion is not trivial - it means free cash flow would have been higher by roughly that margin absent the agency mix. Management framed this as an accepted cost of the channel's growth rather than a problem requiring correction. The stickiness, the channel expansion trajectory, and the long-term margin improvement as agencies shift from social to owned channels are each factors that offset the cash cycle cost.

The social-to-owned channel migration in numbers

To understand why the agency margin story is expected to improve over time, it helps to look at the channel data. According to Zeta's supplemental materials, direct revenue - meaning revenue generated through the Zeta Marketing Platform's own channels rather than through third-party integrations - was 75% of total revenue in Q1 2026, up from 73% in Q1 2025 and within the company's stated 70% to 75% target range.

That directional improvement reflects a gradual shift in revenue mix toward channels where Zeta controls the infrastructure and carries lower media costs. Email, CTV, mobile, and display - all Zeta-owned channels - grew double digits in Q1 2026, and all three use cases (acquire, grow, retain) also grew double digits. The agency onboarding pattern described by Greiner, starting with social and adding owned channels over time, is directionally consistent with the platform-wide trend of rising direct revenue share.

Super-scaled customer additions in Q1 2026 were "especially strong in advertising, marketing, travel and hospitality," according to Greiner. The advertising and marketing vertical accounted for 5% of Zeta's full-year 2025 revenue. Its presence among the strongest-growing super-scaled categories suggests agency-related relationships are beginning to translate into large committed accounts in that cohort.

What this means for the marketing industry

For advertising and marketing professionals, several elements of the agency narrative carry practical relevance. The first is the onboarding pattern itself. Social-first entry, followed by expansion into email, display, CTV, and mobile, is a sequence that reflects how agencies tend to evaluate new technology platforms: they test on a high-volume, easily measurable channel before committing the full account. Zeta's ability to convert those initial social relationships into multi-channel commitments, and now into long-term contracts, suggests the platform is passing that evaluation at a higher rate than in prior years.

The second element is the competitive framing around independents. As the Zeta Global and Yahoo partnership, announced in September 2024, demonstrated, Zeta has been building the data infrastructure to support large-scale third-party relationships for some time. The LiveIntent acquisition in October 2024 added publisher-side identity resolution that further strengthens what Zeta can offer agencies operating across paid, owned, and earned channels simultaneously. Independent agencies that lack the in-house data science and identity infrastructure of major holding companies can now access those capabilities through Zeta's platform.

Third, Athena's role as an agency selling tool marks a product positioning shift. Earlier AI products from Zeta, including the AI Agent Studio launched in March 2025, were more oriented toward platform engineers and campaign managers. Athena is explicitly positioned for business leaders - CMOs and marketing directors - but its white-label potential for agencies competing in client pitches adds a second commercial surface. An independent agency presenting an AI-native platform to a prospective client is pitching a capability that its larger holdco competitors have spent years and billions building internally.

Financial context: what the quarter added up to

The agency-driven cost of revenue increase, the working capital headwind from longer payment cycles, and the investment in Marigold integration combined to produce adjusted EBITDA of $66.1 million at a 16.7% margin in Q1 2026 - 100 basis points below the year-ago margin. But the revenue beat of $26 million above guidance midpoint, the $66 million RPO increase, and the guidance raise of $30 million for the full year each reflect a business where near-term margin compression was accepted as a byproduct of channel mix expansion with a clear improvement trajectory.

Full-year 2026 adjusted EBITDA guidance of $397.3 million at a 22.3% margin - up from 16.7% in Q1 - implies that the social-to-owned-channel migration and Marigold synergies are expected to deliver significant margin recovery through the second half of the year. Q4 2026 is guided to a 25.9% adjusted EBITDA margin, which would represent the highest quarterly margin in the company's history.

For Q2 2026, Zeta guided to revenue of $420 million at the midpoint - 36% year-over-year growth - and adjusted EBITDA of $86.6 million at a 20.6% margin, up 155 basis points year-over-year. That sequential margin expansion from Q1's 16.7% to Q2's expected 20.6% is the first visible step of the recovery that management has described as being driven, in material part, by the maturing of the agency relationships signed in Q1.

Timeline

Summary

Who: Zeta Global Holdings Corp. (NYSE: ZETA), an AI Marketing Cloud founded in 2007 by David A. Steinberg and John Sculley, headquartered in New York City. The company serves enterprise clients and, increasingly, advertising agency holding companies and independent agencies as technology infrastructure partners.

What: Zeta's Q1 2026 results, reported April 30, 2026, revealed that new agency wins were the primary driver of a 190 basis point increase in cost of revenue - because agencies enter the platform through social, the highest-cost channel. At the same time, among the five largest holding companies, brand count grew 50% year-over-year, one large independent agency moved from zero to eight-figure revenue in a single quarter, a second agency signed a contract more than ten times its prior-year spend, and agencies began signing long-term committed contracts that contributed to a $66 million RPO increase.

When: The Q1 2026 earnings were announced on April 30, 2026, covering the quarter ended March 31, 2026. The agency dynamics described reflect Q1 activity and management's stated expectations for the remainder of 2026.

Where: Zeta is headquartered in New York City. Agency relationships span global holding companies with operations across North America, EMEA, and APAC, with Zeta's platform delivering cross-channel activation including social, email, display, CTV, and mobile.

Why: The agency channel matters to the marketing industry because the pattern Zeta is describing - social-first onboarding followed by migration to owned channels, combined with long-term contract conversion and Athena as a white-label AI layer - represents a particular model of how AI-native marketing infrastructure can serve agencies competing for enterprise clients. The cost structure of that model, including higher near-term cost of revenue and longer payment cycles, is visible in Zeta's Q1 financials and offers a concrete data point for how the agency-as-channel strategy plays out operationally.

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